Follicles were collected from ovaries removed under halothane anesthesia from 7 rhesus monkeys. Follicle and ovum diameters were measured and chromatin organization was determined by fluorescence microscopy. The relative growth curve of oocytes and follicles using a local regression technique displayed a triphasic curve. The ovum diameter increased rapidly from <65 m to 85 m in proportion to an increase in follicle diameter from 100 to 175 m. In the second phase the ovum growth slowed (from 85 to 100 m) in relation to follicle growth (from 175 to 400 m). In the third phase the oocyte grew from 100 to 120 m with a marked relative increase in follicle size from 400 to 8000 m. The relationship of follicle and oocyte growth and oocyte maturation (perinucleolar chromatin configuration) was analyzed. Chromatin organization progressed in relation to ovum size. In terms of follicle size, oocytes first respond (past the unrimmed nucleolar stage) during the period of earliest antrum formation, then the response remains relatively the same until the follicle reaches 500 m when the majority of responders are at the partial rim stage. But it is not until the follicle has reached a diameter